Protective coating for metals



Jan. 1, 1935. B. BANNls'rER PROTECTIVE-GOATING FOR METALS Original Filed June l1. 1'952 a. .A MW

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25 befreduced to that necessary forv mechanical metallic piping and I will therefore describe 25 4.5 natcd and after corrosion starts it is apt to working ro1l. It.wi1l be understood that the rolls 45 enonaa'JonLioss l f T y 1,986,704-,

AUNITED STATES PATENT OFFICE Bryant Bannister, Mount Lebanon, rn.

:continuation or application serial No. 616,609, i June 11, 1932. This application March 14,

1933, sor-uu No.v 660,720

e clams. (ol. 14s- 7) This invention relates to protective coatings chrome and nickel, or of chrome and manganese, for metal articles and particularly for metal pipbut such alloys are far too expensive to be eming, and is a continuation of my co-pending apployed for the usual purposes of steel or wrought plication, bearing the same title, Serial No. iron pipe. I therefore contemplate a process by s 616,609, led June 11, 1932. which it is possible to form a thin protective 5 An object of the invention is to produce a new alloy on the surface of a. base metal such as a and improved method of applying a coating of ferrous metal, although my invention, ln its protective material to the surface of an article. broader aspect, is not limited to the formation A further object is to produce a new and imof an alloy, but generally contemplates providing lo proved method of forming a protective alloy athin impervious and rmly anchored protective 1o coating on' the surface of a metal article such case for an article such as an iron or steel pipe. as a pipe or conduit. In the drawing accompanying and forming a The general use of pipe lines for transporting part hereof I have shown apparatus capable of gas, oil and such liquids over long distances, has being employed in carrying out my invention in l5 accentuated the necessity for providing cheap connection with metal piping. Figure 1 is a 15 piping,y which is durable under varying atmosside elevation of apparatus embodying my inpherlc and soll conditions. The question of exvention, portions being shown as broken away pense renders the use of non-corrosive metals for convenience of illustration. Figure 2 is a in the manufacture of pipe for such purposes transverse View of the apparatus shown in Fig- 2o prohibitive, with the result that the art has necure 1, DOIJiOnS being ShOWIl in Section fOr 00n- 20 essarily turned to ferrous meals, and various venience of illustration. Figure 3 is a sectional attempts havel been made to solve the problem end view taken on the lines III-III of Figure 1. of external corrosion. If assured of corrosion The apparatus illustrated is particularly protection, the wall thickness of the pipe could adapted for applying a protective coating to strength, since extra metal would thenI not be my invention as specifically applied to the coatnecessary to provide forf the expected loss of ing of metallic piping. strength resulting from corrosion. With this in During the operation of manufacturing iron or mind, it isapparent that the resultant saving in steel piping, the billet, after being pierced, is so material and the elimination 'of costly maintegenerally subjected to a reeling operation and/or 3o nance would amply justify incurring considerable an elongating operation wherein the pipe, while expense in providing a corrosion-free pipe. at a working temperature, is subjected to the As stated, the problem of protecting steel or working effect of rolls which engage its external iron piping against external corrosion has been surface. A $5 the subject of considerable research within recent In the drawing, I have illustrated one step of a 35 years but, up tothe present time, the various pipe forming operation which happens to be a methods and procedures advocated have only wall reducing operation. The pipe blank 4 enbeen partially effective. This is primarily due closes a mandrel 5, which is of less diameter than to the fact that it has been` impossible to so the internal diameter of the blank and which is 4o coat iron or steel surfaces with aprotective covfree to move with the blank. The external sur- 40 ering as to avoid scaling or checking of the coverface of the blank is operated upon by oppositely ing or the presence of minute pin holes in the disposed rolls 6 which rotate in the same direccovering. The result of either is detrimental, tion and which cooperate with the mandrel 5 in since the possibility for corrosionV is not elimisuch a way as to constitute the mandrel an idler progress quite rapidly, with the result that the 6 are crossed as shown in Figure 1 and are driven base and the protective surface are damaged by any `suitable means. Under such conditions and a condition is promoted which favors the the blank is not only rotated by the actionof progress of the corrosion. the roll 6 but is also moved forwardly in the dl- 50 Qne of the more specific objects of my invenrection of the horizontal arrow shownn Figure 1. 50

tion is to produce a thin but impervious protec- Guide rolls or disks 'I are employed in the partive alloy on the surface of a metal base. It is ticular reducing procedure illustrated. The apparent that the ideal pipe for corrosion reaxes of these rolls extend at right angles to the sistance, would be composed entirely of corrosion axis of the blank 4 or to the direction of longiresistant material, such as a ferrous alloy of tudinal travel of the blank. These disks arc so 55 located that they take the place of the ordinary stationary guides and are driven at a peripheral` speed considerably higher than the longitudinal motion of the blank 4. As indicated by the arrows associated with these disks in the drawing, the disks are driven' in the same direction and in such a .direction as to give some propelling effect to the blank in the direction of its longitudinal travel, Each disk is grooved, as shown, so that its blank engaging surface substantially con-- forms tothe contour of the pipe blank, although the disks are so located as to allow a small clearance between the inside of the blank 4 and the mandrel 5, as shown in Figure 2.

In the manufacture of wrought iron pipe it has been found that the guide disks should be driven at such a rate as to give them a periph` eral speed much greater than the longitudinal speed of the blank, and this velocity ratio may be as great as one hundred to one in order to obtain or insure a substantially frictionless effect insofar as the rotative movement of the blank is concerned. When dealing with steel, a reduced ratio of velocities may be employed. It will be apparent that under the conditions described, the disks 7 do not change the wall thickness of the blank. They, however, do transform the peripheral elongation of the blank walls into a longitudinal elongation and have a decided burnishing action on the external surface of the blank. Under the speed and power conditions encountered, a tremendous amount of heat is generated at the point of contact between the disks and the blank, and conditions may be so controlled that suiiicient heat will be generated to actually produce a molten illm or. skin on the surface of the blank.

I take advantage of this and also of the fact that the ,disks 'I explore every portion of the blank passing between them, by employingthe disksas spreaders for the coating material. This f material is therefore introduced onto the surface of the pipe blank immediately before lthe surface is engaged by the rapidly rotating disk and is preferably introduced in finely divided formk and at a relatively high temperature.

A It will be apparent that the coating material must have a melting or alloying temperature below the temperature of the tube but a vaporizing temperature above that temperature in order to be most effectively employed. .For example, aluminum or copper dust may be blown onto the tube by pressure nozzles 8, one of which is shown located -withV its delivery aperture immediately adjacent one of the rolls 7 and so directed as to deposit a thin lm of dust on the surface of the tube immediately prior to the time that surface is engaged by the adjacent disk 7. Under such conditions and particularly under the condition referred to, wherein the disks are driven at -such a speed asY to generate suillcient'heat to produce a thin iilmor skin of molten `metal at the surface of the blank, the coating material will not only bespread over the surface of the blank but will form an amalgam therewith, thus producing an atomic bond between .the protective coating and the base metal. y

By base metal Ik mean the metal of the blank and I employ the term throughout this speciiica. tion merely to distinguish between the metal of the blank and the coating material. It will .also be apparent that alloying material such as manganese, nickel and chromium may be delivered to the surface of the blank as above described.

While these materials may be delivered in powg upon.

dered form, it is preferable to deliver them in molten condition and to employ a spray nozzle 8 which is capable of delivering a thin film of molten metal to the surface of the blank at the points indicated in Figures 1 and 2. Where alloying metals are thus delivered the conditions must be such as to the surface of the blank at an alloying temperature and this, as previously stated, can be accomplished by controlling the speed of the disks 7, it being understood that the blank is, under ordinary conditions, maintained at a working temperature, such as is usually employed in pipe piercing and pipe forming operations.

It will be understood that apparatus similar to that employed in spraying molten metal may be utilized in place of the` nozzle 8 illustrated, and that the metal delivered may in itself be an alloy having a relatively high percentage of the alloying material, such as chromium, manganese or nickel, since the alloy so delivered will be somewhat diluted by the molten fllm or skin formed on the blank.

It will be apparent that the protective coating need not necessarily be composed of such material as will form an amalgam or an alloy with the base metal, since the conditions are such that a mechanical bond or an embedment may be relied I therefore also contemplate employing protective materials having a melting point below the encountered temperatures of the blank and a vaporizing temperature above those temperaatomic bond with'the base metal. Under such conditions the disks`7 will not only accomplish the function of spreading the thin film of protective material over the surface of the blank but will also insure an embedment of the film, or the material of which the .film is composed. in the surface of the blank but will also insure a uniformity of the film. That is to say, the action of the disks in connection with the alloying or nonalloying material will be such as to insure the spreading of an impervious coating over the surface of the blank provided, of course, sufficient coating material is delivered to form an impervious and uniform cover.

From the foregoing it is apparent that a protective coating may be firmly secured or anchored to the surface of a base metal, without greatly increasing the cost of the article being manufactured. For example, an alloy, as above described, approximately,.003 inch thick, may be formed on the surface of a 24 inch O. D. x $41 inch wall pipe, 35 feet long and weighing a gross ton, by utilizing approximately four pounds of chromium and two and one-half pounds of nickel in the production of a surface alloy having 18 percent chromium and 8 percent nickel. While the cost of producing such a surface is relatively low, the

pipe so coated will resist external corrosion as effectively as if the entire pipe were made from vthe non-corrosive alloy. It will also be apparent that the coating operationadapts itself to thev material tothe surface.

It win be apparent that while 1 have inustnitea and described my process in connection with apparatus employing rapidly rotating disks as well delivering a thin film of either powdered ormolten g as the working rolls 6, the process may be carried forward in connection with any form of rotating spreading rolls. That is to say, the finely divided "coating material, whether powdered or molten,

may be delivered to the surface of the blank immediately adjacent the working rolls operating on the blank, and particularly where the pressures encountered and the speed of operation is such that the effect of the working rolls is to impart heat to the blank.

It is also apparent that while I have illustrated the invention in connection with pipe forming machinery that the invention is not so limited `and that various changes, additions, omissions and modications may be made in the procedure contemplated, and various substitutions of material may be resorted to, without departing from the spirit and scope of the invention as set forth by the appended claims.

I claim:

1. The method of forming a protective coating on the surface of a base metal which consists in delivering a thin film of coating material to a portion of such surface while maintaining such portion at least at a forging temperature, and then in subjecting the base metal and the coating material to a burnishing action of a magnitude sufficient to generate heat of suiiicient quantity to form a molten film of the base metal and coating material.

2. The method of forming a protective coating on the surface of a base metal which consists in delivering a thin ilm of alloying metal to a portion of such surface while maintaining such portion at least above the alloying temperature of said alloying mgtal, and then in raising the temperature of such portion of the surface by subjecting the base metal and alloying metal to a burnishing action of sufl'lcient magnitude to generate heat of sufficient quantity to form a molten lm of the base metal and alloying metal.

3. The method of forming a ne protective coating on the surface of a base metal which consists in delivering a thin film of alloying material to a portion of such surface while maintaining such portion at least above the alloying temperature of said alloying material and then in helically working said base metal while subjecting the same and the alloying material to a burnishing action of suiiicient magnitude to generate heat of sufcient quantity to form a molten iilm of the base metal and alloying material.

4. The method of forming a protective coating on the surface of a base metal which consists in delivering a thin lm of alloying metal to a portion of such surface while maintaining such portion at least above the alloying temperature of said alloying metal, and then in raising the temperature of such portion of the surface-by subjecting the base metal and said alloying metal to a helical burnishing action of sufficient magnitude to form a molten iilm of the base metal and the alloying metal.

5. The method of forming a ne protective coating on the surface of a base metal which consists in delivering a thin lin of alloying metal to a portion of such surface while maintaining such portion at least above the alloying temperature of said alloying metal, then in subjecting the base metal and the alloying metal to a burnishing action in order to generate heat of suflicient quantity to form a molten alloy lm of base metal and alloying metal, and finally in helically working the molten film to form a complete protective coating.

6. The method of forming a protective coating on the surface of a base metal which consists in delivering a thin film of coating material to a portion of such surface while maintaining such portion at leastat a forging temperature, then in subjecting the base metal and the coating material to a burnishing action of a magnitude sufficient to generate heat of suillcient quantity to at least melt the coating material, and subsequently `working and helically spreading the melted coating material to form a continuous coating onl the surface of the base metal.

BRYANT BANNISTER. 

